Surface heating device

ABSTRACT

A dispensible container constructed for a single use incorporates a thin low voltage heating film with terminals accessible from outside and opening means permitting access to its contents is used as a package for a substance adapted to be heated and plastic in the sense of being sufficiently mobile to be removed from the container as soon as it has been sufficiently heated. The outer portion of the package may comprise means for directing most of the heat inside the package to heat the substance and its side walls may be stiffened by a stiff frame of light weight material of the stressed skin type.

United States Patent Eisler Aug. 7, 1973 [541 SURFACE HEATING DEVICE 2,764,664 9/1956 Stewart 219/411 X 1 1 Inventor: Paul E19", 57 Exeter My London. 335133133 13/1323 5 211151111111... 11111..""519153 England 3,062,663 11/1962 Furgal et a1... 219/385 ux Filed: Mar. 1971 3,079,913 3/1963 Nelson 99/171 H 1 1 pp N05 1221495 Primary ExaminerE. A. Goldberg Rdated US Application Data Assistant Examiner-B. A. Reynolds [60] Division ofSer. N0. 607,601, DCC, 30, 1966, Pat. N0. Brow" 3,573,430, which is a continuation-in-part of Ser. No. 301,488, Aug. 12, 1963, Pat. No. 3,296,415, which is [57] ABSTRACT i i g i g g gg fi July A dispensible container constructed for a single use incorporates a thin low voltage heating film with termi- 52 U.S. c1 219/201, 99/1, 99/171 11, nals,accessible 9 Outside 3 Pening means mittlng access to Its Contents 15 used as a package for 51 161.01. H05b 3/06 Substanc": n be heted and [58] 1 16166: Search 219/201, 385, 386, Sense bemg suffic'emly mb1le be mm/ed 1mm 219/521 477, 1 0 288; 99 171 H the container as soon as it has been sufficiently heated. The outer portion of the package may comprise means [56] References Cited for directing most of the heat inside the package to heat UNITED STATES PATENTS the substance and its side walls may be stiffened by a v stiff frame of light weight material of the stressed skin 2,879,367 3/1959 McLean 219/385 type 2,850,391 9/1958 Gunsberg 99/171 H 2,759,830 8/1956 Touceda 219/354 UX 8 Claims, 55 Drawing Figures Pia tented Aug. 7, 1973 14 Sheets-Sheet 1 INVENTOR R v.1 E15 1 av:-

A'TTQRNEY I Putented Aug. 7, 1913 3,751,629

14 Sheets-Sheet 1 'NVENTOR W MJ Exsler A QN EY Patented Aug. 7, 1973 14 Sheets-Sheet 5 lNvEN-roQ ATTOQNEY Patented Aug. 7, 1913 3,751,629

14 Shuts-Shoot 4.

INVENTQR ATTOQN EY Patented Aug. 7, 1973 l4 Sheets-Sheet 5 INVENTOR R E is aw ATTQRNEN Patented Aug. 7, 1973 3,751,629

14 Sheets-Sheet 6 339, age 329a 323a i F/GJO INVENTQR R E s \QY Patented Aug. 7, 1973 3,751,629

14 Shoots-Sheet 'I gc g/coo aac/ INVENToR Rug E\ S aw ATTORNEY Patented Aug. 7, 1973 14 Sheets-Sheet 8 /A/%\/V /A A A M/A /A A V/A @Ww/W/ v INVENTOR 0ml E i Haw gewwseamm ATTORNEY Patented Aug. 7, 1973 14 Sheets-Sheet 10 Rw\ \NEEITZTZW $BYWQM1 ATTORNEY Patented Aug. 7, 1973 3,751,629

14 Shuts-Sheet 11 in; 5 l 388 F/a4O lNveN'roR QM, Ei 3 I (i v ATTogzNlY Patented Aug. 7, 1973 I 14 Sheets-Sheet ll lNven'rok 1 0ml E1516 BY ATTQRN EY Patented Aug. 7, 1973 3,751,629

Q 14 Shanta-Sheet l4 luvsu-roa @wl E1316 ATTORNGY SURFACE HEATING DEVICE This application is a division of my application Ser. No. 607,601 filed Dec. 30, 1966, now U.S. Pat. No. 3,573,430, itself a continuation-in-part of my application Ser. No. 301,488 filed Aug. 12, 1963 for Surface Heating Device (now matured into U.S. Pat. No. 3,296,415) which was itself a continuation-in-part of my application Ser. No. 749,554 filed July 18, 1958 for Surface Heating Device (now matured into U.S. Pat. No. 3,100,711).

The invention relates to the heating of substancescontained in packages of relatively small size. Foodstuffs in single or multi-portions for immediate consumption are a convenient example illustrative both of the order of size and the kind of substance but the invention is not restricted to this example and can be applied to many other substances which it may be desirable or necessary to heat in the package, as for example, adhesives, coating materials, synthetic resins and similar thermosetting or thermoplastic materials, greases and chemicals. Hereinafter foodstuffs will usually be referred to for convenience.

The present invention provides for a substance to be heated while contained in a dispensible container included in a package to which end a thin low voltage heating film is incorporated in the package at least during the heating operation, this film having a surface pattern presenting a resistive electrical path between at least two terminals to which access can be obtained for connection to a supply without removing the substance from the container. Thus by making connection of the terminals to a supply having a voltage appropriate to the resistance of the path heat can be generated in the film by which the substance can be heated. One object of the present invention is to enable such an arrangement to be used to-heat the substance rapidly without any risk of hot spots in the conductive pattern which might damage the material, damage the pattern or have other undesirable results.

If it could be ensured that the whole conductive pattern were in intimate contact with the substance so that direct conduction of heat into the substance took place, the temperature gradient would be small, there would be no local hot spots and the permissible rate of heating would 'be limited essentially only by the heat conductivity of the substance and the time necessary for the substance to reach the required temperature. In practice however the conductive pattern usually cannot be allowed to come into direct contact with the substance because such contact may be undesirable for electrical reasons or on account of the nature of the substance and material of the pattern, for reasons of packaging, use or processing or storing of the substance, etc. There will usually therefore be at least one thin layer of material between the pattern and the substance to insulate the former and protect the latter; there may be more than one such layer as will appear later. Also it may be necessary for the pattern of the film to extend to parts of the container which are not or may not remain in direct contact on their external surfaces with the substance or even extend outside the container altogether, so that from these parts of the film heat can be dissipated only by radiation or possibly by radiation with some convection. Shortly stated therefore the dissipation of heat from the film in general will not be a simple function only of its area, and

there will be a serious risk of local hot spots if a uniformly distributed resistive pattern is uniformly supplied with current without consideration of any differentiation required by the particular conductive heat transfer into the substance.

For reasons of efficiency, and it may be to enable the package to be handled in comfort, it is desirable that as much of the heat as possible should be dissipated with the substance and as little as possible in other directions.

According to the present invention the problems thus presented are solved by dimensioning the pattern so that in operation in addition to the dissipation into the substance no part of the pattern has to dissipate more than 4 watts per square inch, or in other words when the pattern is connected to a supply to the appropriate predetermined voltage the difference between the heat dissipated into the substance in the container from any area of the surface of the heating film and the wattage supplied to said area is less than 4 watts per square inch of said area, while means are also included in the package ensuring that when the'film is energised more heat is dissipated into the substance than reaches the external surface of the complete package. While such a difference may not be critical in any absolute sense, extensive investigations have shown that under such conditions rapid heating by a dispensible heating film without hot spots or damage becomes possible.

Depending on the manner in which the substance and the film are disposed in relation to one another during operation and the disposition in relation to one another during operation of layers which comes between the actual conductive pattern and the substance itself it may be possible to use a film the loading of which is uniformly distributed over the whole patterned area, or it may be necessary to vary the loading in different parts of the film.

To assist in controlling the relative rate of dissipation of heat into the substance and to the external surface of the package, in some cases the film may be spaced a substantial distance inwardly from the external surface of the package, and the space thus left may be at least partly filled with thermal insulation; The package may include a wall having a flexible, thin, impervious andheat resistance inner layer, e.g., of metallic foil, and means ensuring intimate contact of the heating film with the outside of said layer'at least when the film is connected to the supply.

.A development of the invention provides for some other substance to be carried ona common supporting means such as a tray, thermal insulating means being provided whereby heat reaching the external surface of the package is hindered from reaching the further substance, thus for example enabling meals to be prepared consisting of both hot and cold foods.

A further object of the invention is to provide a heater additional to the heating film and so to construct a wall of the package that the heating of the substance can be supplemented by heat radiated by the additional heater.

Another object is to include means in the heat path between the film and the substance whereby the surface temperature at any point on the substance is prevented from rising above a predetermined maximum value, e.g., a value at which it is damaged or develops some undesirable characteristic such as stickiness. Thus at least during part of the heating period the film may be spaced from the surface of the substance to be heated thereby, and a small body of liquid may be present in the space which has access to the substantial area of the substance so that the temperature of the substance is kept down to boiling point of the liquid. This provision for the presence of liquid between the heating film and the substance is well adapted for us with deep frozen substances. The deep frozen substances may be enclosed within the container at least by a wrapper of metallic foil having perforations distributed thereover, a further substance which boils when heat is supplied also being included in the package and having access to the perforated foil. Such a package may be supplied separately from a heating film so that the two can be put together for use, or the package be heated by some conventional heater such as a gas or electric cooker.

Still another object of the invention is to enable the heat supplied by the film to be supplemented by conducted heat from another source, to which end a heat conductive flexible wall with one surface in contact with the substance, may have in contact with its other surface over a substantial area a plate equipped with means for supplying heat to it under the control of a temperature sensing element within the plate whereby the temperature of the plate is maintained within known limits, so enabling heat to be supplied to the substance at a rapid rate without the risk of local hot spots or temperature rises.

It may here be mentioned that for the purposes of this specification and in the claims dispensible containers means not that the container has to be dispensed with for technical reasons such as destruction being necessary for access to the contents but that it is economically dispensible. Generally speaking food and many other substances are packaged in containers the cost of which in comparison with the cost of their contents makes it economically feasible to dispense with them once opened, a highly desirable possibility from the hygienic point of view at least in the case of food. The films used in the present invention can also be produced sufficiently cheaply to enable them to be dispensed with, and their nature will generally be such that their cost will be lower than the cost of collecting, cleaningand reconditioning (e.g., sterilizing) and reassembling with other partsof the package so that there will be noincentive to attempt their recovery which would generally be undesirable at least in the case of food. I

As will be shown they may be made of materials such as metallic foils which are commonly used in packaging, sometimes with the addition of such material as carbon e.g., graphite which in the quality and quantity required is also very cheap.

As mentioned above the films are designed to operate on a low voltage which is not dangerous to human contact generally below 50 volts and preferably a good deal below 50 volts. This not only avoids danger, but considerably cheapens the film by avoiding the need for high cla'ss insulation. The low voltage may advantageously be the same as that of the usual motor car battery, namely I2 volts. Voltages of this order enable meander patterns of very convenient dimensions to be used in practising the invention.

Further objects and features of the invention will become apparent from the following description with reference to the accompanying drawings. The drawings are diagrammatic and in particular where the heating film or other material is shown in section in most cases thicknesses are much exaggerated.

FIG. 1 is a perspective view and FIG. 2 a cross section of a moulded trough-like dispensible container according to the invention.

FIG. 3 illustrates the heating film used in FIGS. 1 and 2.

FIG. 4 illustrates the production of a heating film for a folded container.

FIG. 5 is a plan of the blank from which such a container can be made.

FIG. 6 is a perspective view of the folded container.

FIG. 7 is a perspective view and FIG. 8 a cross section of another folded container.

FIG. 9 is a perspective view and FIG. 10 a section of yet another folded container.

FIGS. 11 and 12 illustrate the production of a heating film with two branches.

FIG. 13 is a vertical section ofa dispensible container for heating and dispensing a batch of liquids.

FIG. 14 is a circuit diagram of the container of FIG. 13.

FIG. 15 is a perspective view and FIG. 16 is a detail section'of another dispensible container for heating and dispensing a batch of liquids.

FIG. 17 is a perspective view and FIG. 18 a section of a dispensible container in which the heating film also indicates the quantity of substance removed.

FIG. 19 is a section of an embodiment which provides for movement of the heating film in relation to the contents of the container.

FIG. 20 is a perspective view, partly in section of a further development for steaming or similar heating a substance.

FIGS. 21 and 22 are detail sections of FIG. 20.

FIG. 23 is a detail similar to FIG. 21 of an alternative to FIGS. 20 to 22.

FIG. 24 is another detail of this alternative.

FIGS. 25 and 26 show two stages in the use of a dispensible container in which the configuration of the heating film is changed between stages.

FIG. 27 is a perspective viewof a container the contents of which are to be heated by radiant heat.

FIG. 28 is a perspective view showing the container of FIG. 27 in position prior to heating. I

' FIG. 29 is a perspective view and FIGS. 30 and 31 are details of a further development for radiant heating.

FIG. 32 is a section of another container the contents of which are to be heated by a contact heater.

FIG. 33 is a detail of a modification of FIG. 32.

FIG. 34 is a detail section and FIG. 35 a perspective .view of an arrangement for heating a substance while maintaining another substance on the same support cold.

FIG. 36 is a perspective view of a more elaborate arrangement for the same purposes as that of FIGS. 34 and 35.

FIGS. 37 and 38 are details of FIG. 36.

FIGS. 39 and 40 are a plan and cross section of one of the trays used in this arrangement, the former with no food container in place.

FIG. 41 is another detail.

FIG. 42 illustrates a plant which may be used for processing food during packaging in containers according to the invention.

FIG. 43 is a detail side view and FIG. 44 is a plan view of clip device making connection to a heating film.

FIG. 45 illustrates the terminals of the film for which the device of FIGS. 43 and 44 is designed.

FIG. 46 is a detail longitudinal section of FIG. 44.

FIG. 47 shows a circuit using the device of FIGS. 43 to 46.

FIG. 48 is a longitudinal section of a plug and FIG. 49 is a longitudinal section of a socket for making connection toa clip device for connection to the heating film.

FIG. 50 shows a form of heating film which can be used in the invention.

FIG. 51 is a sectional plan and FIG. 52 a sectional elevation of a form of package within the scope of the invention.

FIG. 53 is a cross section of a heating film which can be used in the invention, embodying a carbon film.

FIG. 54 is a plan of the electrodes and FIG. 55 a section of another form of heating film embodying a carbon film.

A convenient form of container used in a package according to'the present invention is a trough like box made of moulded papier mache or similar material or folded from cardboard, paper or the like, the heating film being made integral with a folded-over unpatterned portion which forms an impervious cover layer which serves to enclose the substance in the container notwithstanding that the other material of the package maybe porous, a thin electrically insulating layer coming between the folded-over portion and the pattern. The papier mache or folded cardboard, paper or the like is a relatively stiff fibrous material and it forms a thermally insulating layer, while the thin insulation and plain folded-over portion do not impose any great thermal resistance between the pattern and the packaged substance.

FIG. 1 is a perspective view and FIG. 2 a cross section of an' open trough like box which may be moulded of such material as papier mache. The heating film itself is made from metallic foil of the general form shown in FIG. 3. It consists of a plain part 81 integral with a patterned part 82. In the figure a single meander path is formed by the pattern between thecentral zone and onemarg'inof the complete piece of foil, but this is only one variety; generally the pattern comprises a number of repeats; The part 81 is of somewhat greater length than the part 82. A thin layer of insulating material for example paper of somewhat less width than the portion 82 but greater length is laid over it"as indicated by the dotted line 83 and the portion 81 is then folded over the insulating material on the line 84. This portion is of less width than the insulation 83,and thus after folding itsedge is overlapped by the insulation. The margin of the portion 82 extends beyond the edge of the insulation 83. The foil and insulation may be held together by adhesive. The film so made is depressed into the trough like box and the edges are lapped over the edges of the box as indicated by the cross section FIG. 2, the dimensions of the film being designed so that the fold at 84 reaches just under the edge of the box, the edge of the portion 81 remains wholly on top while the projecting margin of the portion 82 is also lapped over the edge of the box. These two margins thus constitute the terminals of the pattern and connection can be made by means of a clip such as described in my U.S. Pat. No. 3,100,711.

The length of the patterned portion 82 may be such that it lies wholly within the box while the length of the portion 81 is such that it extends over the end walls of the box and over the upper edge. There will-be some puckering of the portion 81 at the corners but this need not damage it and the foil will form an impervious lining which covers the slots in the pattern and is of good heat conductivity. The folding of this portion to fit the container may be facilitated by crimpingthe material and such crimping may also extend to the patterned portion 81 or the latter may be plain while only the portion 82 is crimped. After the box has been filled the open top may be closed by a cover held by adhesive and this may be arranged actually to press the packed substance against the heating film. Instead of a simple cover a second similar box can be used and the two be secured together by adhesive at the margins but the terminals of the films will need to be brought further out to permit connection to be made.

FIGS. 4 to 6 illustrate a somewhat similar container to FIGS. 1 to 3, but produced by shaping, scoring and folding of flat stiff fibrous thermally insulating material such as cardboard, incorporating the heating film. As before the film itself is made of a doubled piece of foil comprising a plain part85, a patterned part 86, and a layer of insulation 87 between the two portions. After the film has been made, it is laid on (and may be laminated to) a sheet 88 of cardboard of similar material which has been slotted as at 89 and creased at the dotted lines 91. Thereafter the assembled material is folded at the crease lines and in the corners in the wellknown fashion to produce an open box as in FIG. 6.

The laminated packaging material can be produced in a web and is cut up in pieces for shipping as flat stock to be erected into a box when the box is filled. It can instead be supplied in the web, and the plain parts 85 which are to form the impervious inner layer of the box can be left uncrimped, if desired, although the patterned parts 86 may be crimped.

It will be seen in FIG. 5 that the margin of the patterned part 86 extends furthermost to the right, that the insulating sheet 87 does not extend quite as far while the edge of the plain part 85 of the foil does not reach quite to the edge of the, paper sheet 87, but all these so that both terminals areslightly overlapped by the paper 87..As before the patterned part 86 does not ex.- tend beyond the ends of the bottom of the box but the plain part covers the bottom and all four walls of the box. The box may be closed by a plain cover or two boxes may be used together if provision is made for access to the terminals.

If it is necessary or desirable to provide for the substance in the box to be heated from the top as well as the bottom as shown in FIGS. 7 and 8 a folded box may be produced having an integral hinged lid 92, a heating film 93 extending into the lid. The film itself is made on the same lines as in FIGS. 4 to 6 the dimensions being modified and the terminals are brought out exactly as in FIG. 6. The shape, slotting and creasing of the cardboard or similar material and the manner of folding are in themselves wellknown and need not be described further. With this arrangement connection to the film can be effected without opening the box but if preferred the margin with the terminals can be folded inward so that the box must be partially opened to gain access to the terminals though they may then be folded outward. The package may be sealed with the terminals folded in and the lid sealed so that the purchaser has to destroy the seal to obtain access to the terminals.

Other schemes for supplementing the heat supplied by the heating film, including supplementary heating from the top are described later.

For packaging and heating a liquid, a box as shown in FIGS. 9 and 10 may be used. Such a box again is of wellknown form and can be produced by folding from a blank of suitable shape on very similar lines to FIGS. 4 to 8. A heating film 94 with accessible terminals 95 is incorporated and the patterned area extends up to the level 96 while the liquid level is at 97, so that it wholly covers the area of the film in which heat is developed.

By suitably changing the dimension and proportions of the blank various other folded box type containers can be produced and similarly moulded containers on the lines of FIGS. 1 to 3 can be produced with different proportions. A moulded container can be provided with a heated lid by extending the film into a moulded lid.

A particular difference between a moulded container and a folded container is that the latter necessarily has sharp corners at the folds while a moulded container can be produced with rounded corners which may be more desirable in some cases. Where the heating film extends into the lid the pattern may be dimensionsed so that the heat developed per unit of area is different in the lid from what it is in the bottom of the container.

FIGS. 1 to 10 show the heating pattern consisting only of one meander path. This is done for sake of simplicity of drawing; each pattern can consist of a group of equal or different repeats, i.e., meander paths in parallel. These examples also assume a pattern of a single resistance or resistance grouping between two terminals and thus a single rate of heating and of heat distribution to the contents of the container under a specific supply voltage. A pattern with two branches having its terminals disposed to' have connection made toit by a suitable clip (as described with reference to FIGS. 16,17 and 18 of my U.S. Pat. No. 3,296,415) may be made as illustrated in FIGS. 11 and 12. A piece of foil (which again may be cut from a continuous length bearing'a repeating pattern) has two patterned margins 98 e'ach'with a half lengthtab 99 at the extreme edge these tabs being relatively longitudinally staggered. The foil is scored and folded at its longitudinal centre line 101 and again at two longitudinal lines 102. Two pieces of sheet insulation e.g., paper are introduced. One

dimensions of the film and position of the score lines 101, 102 are such that the fold at 101 does not reach to the outer edge of the insulation 104 so that the latter effectively insulates the plain part of the foil over the upper pattern. The two tabs 99 constitute terminals while the zone of the plain part of the foil adjacent the fold 101 constitutes a common terminal. It will be clear that a heating film so made can be used for example in boxes such as those described wtih reference to FIGS. 1 to 10 and that the plain parts of the foil can be made longer to cover the end walls of the. box. They can also be used in the heating of liquids at the time of dispensing from a storage vessel as described below.

An arrangement which enables specific quantities of liquid to be drawn out of a storage vessel and then heated before being dispensed comprise a tube having one end portion adapted to be inserted into the vessel, another end portion for discharge and between the end portions an enlargement of such volume as to contain at least one batch of the liquid. Suction is generated at the discharge end of the tube by sucking, by squeezing the flexible tube walls or otherwise and flow control means enable this to be used at choice to draw liquid from the vessel into the enlargement and to draw liquid from the enlargement through the discharge end. The dispensible heating film is in good contact with tube wall at least over the major part of the enlargement and the whole device constitutes a dispensible container. Flow control means may be combined with switching means for the heating film whereby the current can be varied according to whether liquid is being drawn into the enlargement or out of the enlargement, the film then having a pattern with at least two branches as described above.

FIG. 13 shows a device on the above lines. The tube 109 carried for example by a cork or similar stopper 1 l 1 and long enough to extend to the bottom of a storage vessel such as a bottle has a portion 1 12 of enlarged diameter above the stopper and of a volume to contain one batch to be dispensed. In good heat conductive contact with the wall of the enlargement 112 is a heating film 113 having two branches the terminals being brought out and connection being made by a clip 114. However there need only be two terminals and two contacts on the clip as the control of the flow through the two branches is not effected through the clip but by means of a draw-off tube 115. The draw-off tube is a sliding fit in the contracted upper end of the enlargement. To draw liquid into the enlargement the tube 115' is brought into its uppermost position shown in FIG. 15, when a fitting 122 ensures asufficiently airtight closure of the enlargement. Suction on the outer end of the tube 1 15 will now draw liquid into the enlargement 112 and if the outer end is now closed by the finger the liquid will remain in the enlargement while'the tube 115 is depressed until a conical fitting 116 at its lower end seats in the bottom of the enlargement and thus prevents liquid from running back into the bottle. There is a hole 117 in the tube 1 15 which is just above the fitting 116 so that if now suction is applied to the outer end the liquid will be drawn through the hole 117 into the tube 1 l5 and out of its upper end, air entering between the tube 115 and the contracted end of the enlargement, a groove being provided if necessary for the passage of air.

There are two contacts 118 at the lower end of the enlargement which are bridged electrically by the fitting 116 in the lowered position of the tube 1 15. There are two separate pairs of contacts 119,121 at the upper end of the enlargement which are separately bridged by the fitting 122 on the tube 115 when this is in the position shown in FIG. 13. The circuit is shown in FIG. 14. With the tube 115 in the position of FIG. 13 for drawing liquid into the enlargement there is no bridge across the contacts 118, consequently the supply passes from the lower of the terminals 123 first to the contacts 119 which are bridged by fitting 122 and thence to a terminal common to the two branches 124 of the heating film and then through the contacts 121 also bridged to the other terminal of the supply. Thus the two branches are in parallel and the maximum rate of heating is achieved. After the liquid has been heated as desired the tube 115 is depressed and in its lowermost position contacts 119 are disconnected, contacts 121 are disconnected, but contacts 118 are bridged. Accordingly the lower terminal of the supply is connected to the upper end of one of the branches 124 and the upper end of the other branch 124 is connected to the other terminal of the supply. The two branches are thus con- I nected in series and the rate of heat development is therefore reduced to a quarter of what it was before serving to maintain the temperature of the liquid which will slowly rise or fall depending on the conditions of the particular case. Suction can be applied by any means but it is contemplated that this device is generally to be used for a beverage to be consumed by suction applied by the mouth after the fashion of a drinking straw. I t g The device illustrated in FIGS. and 16 enables suction to be generated by the device itself more conveniently than in the device of FIG. 13.

In this case there is again a tube, marked 125 which reaches to the lower end of the storage vessel 126. It is shown passing through a closure in the top of a bottle but might carry a cork or the like as in FIG. 13. The tube 125 communicates with the upper end of an enlargement 127 which is made of cheap flexible material, e.g., polythene."I-he enlargement is equipped with a discharge'tube 128 which reaches practically to the bottom, but'also has an aperture 129 near its upper end, just under the flexible top 131 of the enlargement. Close by is an aperture 132 in the top 131 with a flap 133 which can close it but which tends to spring open. Round the enlargement 127, in good heat conductive contact with it, is the dispensible heating film 134 provided with a two branch pattern. Connection is made toone branchby a clip 135,3the pivot 136 of which is tubular and serves to holdfth'e clip and enlargement together by passing the tube 125 through the pivot. jThe second branch of the film pattern has a terminal area 137 covered at its-end, near theclip attachment, by'thin' insulation 138 such as paper andover this isa piece v139 of spring foil with whichthe clip makes contact and which overlaps the paper 138 but normally springs away from the terminal area 137.

In use, by closing apertures 129 and-l32 by finger pressure on the top 131 and flap 133, and applying suction to the end of the discharge tube 128 liquid can be drawn out of the vessel, 126 into the enlargement 127. If the flap 133 is now released while the aperture 129 is held closed, continued suctionwill draw liquid out of the enlargement 127 and the tube 128 Alternatively theenlargement can be squeezed to drive out air, the apertuers 129, l32-and the dischargeend of the tube "She closed and the enlargement then released when its expansion will generate suction which will draw someliquid up into the enlargement and this pumping action can be repeated until the enlargement is full. Then further squeezing with both apertures closed will discharge liquid from the enlargement through the tube 128.

One terminal of the film will be in circuit as longas the supply is connected, while the other can be brought into action by pressing the foil 139 into contact with the terminal area 137. The fact that these foils are bare does not matter with a low supply voltage of say 12 volts. Both' branches are brought into operation for. rapid heating of the liquid when the enlargement is full, and one branch to maintain the temperature during the discharge of the enlargement. Alternatively the clip and terminal pattern of the film may be as described above with reference to FIGS. 11 and 12 to enable the heat dissipation to be varied.

The devices shown in FIGS. 13 and 16 can readily be produced by moulding such a material as polythene and will be cheap enough to be dispensible. Their shapes may vary considerably from those shown without any change in their operation. They may also be made of other materials and by other methods without any change in their operation, for example of folded paper or the like of a quality which remains impervious for the necessary period of use.

A dispensible container and dispensible heating film according to the invention can also be used in cases in which only part of the contents of a package are to be.

used at a time, in which case the film can be provided with means visible from the outside indicating the proportion of heated substance removed from the container. For example the film may be wrapped round the substance and have one end held under tension so that when some of the substance has been withdrawn, the film is drawn close to the reduced volume of the-substance, a corresponding length of the film being drawn out of the container and serving as a measure of the removed substance.

As shown in FIGS. 17 and 18 a dispensible container 141 of somewhat similar form to that shown in FIGS. 9 and 10 and which could similarly be made of folded paper or cardboard is equipped with a heating film 142 which surrounds a flexible bag 143 containing the substance 144 to be heated but is not stuck to the inside of the container. The container'has a narrow aperture 145 of its full width andone edge 146 of the film is se cured to the edge of the aperture, while the .inargi'n 147 at the other edge incorporates the terminals and passes through the aperture. When the container is full (FIG.18) this only need emerge enough topermit access tothe terminals by a clip 148 through" which connection is made. Before use,.this margin maybe folded over and covered with a seal of paper or the like. The

container also has provision for withdrawing heated 7 holds the film in tension. When some of the heated substance is removed, a corresponding length of the film is drawn out and it is calibrated with markings indicated at 151 showing what proportion has been removed.

hot 

1. A package comprising in combination, a dispensible container constructed for a single use to hold a removable plastic substance, a substance held in said container adapted to be heated while supported within the container and to be removed as soon as it has been sufficiently heated, a thin low voltage heating film having a surface pattern presenting a resistive electrical path between at least two terminals incorporated in said container with the terminals constructed of a portion of the heating film surface pattern extending from and accessible from outside the closed container for connection to a current supply without removing said substance from said container, opening means for permitting access to the substance in the container after it is heated and an external radiant heater, said package including a wall disposed opposite the radiant heater of a material having at least an external surface of good radiant heat absorption factor whereby radiant heat is transmitted through said wall to supplement the heat developed by the heating film.
 2. A package as defined in claim 1, wherein the outer portion of the package comprises heat stable foil means for directing most of the heat inside said package to heat the substance and transmitting radiant heat to the substance inside the container from said radiant heater.
 3. A package as set forth in claim 1, and means included in the heat path between the heat generating surface of the film and the substance whereby the surface temperature at any point on the substance is prevented from rising above a predetermined maximum value.
 4. A package as set forth in claim 1 wherein at least during part of the heating period the heating film is spaced from the surface of the substance to be heated thereby.
 5. A package as set forth in claim 4 also including means ensuring that at least after energization of the film and before any part of the substance reaches a temperature at which undesirable changes occur in it, a small body of liquid is present in the space between the heating film and surface of the substance, said liquid having access to a substantial area of the substance.
 6. Apparatus as defined in claim 1 wherein said radiant heater includes a closable receptacle compartment for receiving said package.
 7. Apparatus as defined in claim 6 wherein said compartment includes a drawer movable in and out of said compartment to receive said package.
 8. Apparatus as defined in claim 7 wherein said drawer is wedge shaped and said compartment includes activation devices actuated by wedge action to activate said radiant heater when said drawer is moved into said compartment. 